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12th Biology 2013 Set2 Delhi Board Paper Solution

Question 29

A child by the family from Thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby. (a) What is Thalassemia?
(b) How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.
(c) List the values your counselling can propagate in the families.

Answer
(a) Thalassemia - is an autosomal reccessive blood disease which can occur due to deletion of the genes controllign the formation of globin chains (commonly Alpaha and Beta) of haemoglobin.
 
(b) Mother cannot be blamed for the disease as, it is an autosomal reccessive blood disorder. The genes for the synthesis of globin chains are present on autosomes i.e.
 
(i) Formation of Alpha chain is controlled by 2 genes present on chromosome 16 and
(ii) Formation of Beta-chain is controlled by one gene present on chromosome 11manifestation of the disease occurs when the progeny receives defective genes from both the parents (as thalassaemia is expressed is homozygous recessive condition only).
 
(c) Values that can be propogated in families are
 
(i) One should be aware of such autosomal diseases ad should get themselves checked for the same before marriage.
(ii) Manifestation of the disease occurs due to defective genetic set up of both the parent (so it is not only mother to be blamed.